SOYBEAN AND HEALTH - University of Macau Library

468Soybean and HealthCompounds BRS 133 a BRS 258 b OCEPAR-19 c UFV-116 d UFVTN 105AP e USDA fProtein 37.4 42.3 41.1 39.4 46.2 39.9Lipid 21.4 22.7 24.6 20.8 19.9 21.4Ash 4.9 4.8 4.7 6.6 5.3 5.2Insoluble dietary fiber 23.2 23.0 0.7 0.8 9.1 ndSoluble dietary fiber 2.8 2.8 1.7 1.3 1.5 ndTotal dietary fiber 26.0 25.8 2.3 2.1 10.5 9.9Total carbohydrates 36.3 30.1 28.0 23 13.8 32.3Linoleic (18:2) 5.6 5.6 5.5 5.5 5.8 9.9-Linolenic (18:3) 0.9 0.7 0.8 0.8 0.7 1.3nd: not determined; a Soybean with low protein content and with hull; b Soybean with high proteincontent and with hull (Paucar-Menacho et al., 2010); c Conventional soybean with hull thermally treated 80oC for 20 minutes; d Soybean without LOX 2 and 3, hull-less, thermally treated 80 °C for 20 minutes(Esteves et al., 2010); e Soybean with high protein content without LOXs, with hull, thermally treated 150°C for 30 minutes (Andrade et al., 2010); f Conventional soybean (U.S. Department of Agriculture, 2009).Table 17.1. Chemical composition of conventional and genetically improved soybeans (g/100g).The main soluble carbohydrate of immature soybean is glucose. With the maturation of thegrain, this sugar disappears, predominating non-reducing sugars such as sucrose, raffinoseand stachyose (Paula, 2007). Most of the complex polysaccharides and oligosaccharides of thegrain are composed of fibers, which are located mainly in cell walls and interstitial material ofthe shell (86%). The cell wall of soybean contains about 30% pectin, 50% hemicellulose and20% cellulose. The grain also contains approximately 1% starch (Liu, 1997).Soybean presents a high lipid content and is good source of essential fatty acids. In somesoybean cultivars it has been observed they contain approximately 63% polyunsaturatedfatty acid, 55% linoleic acid and 8% linolenic acid; 21.5% monounsaturated fatty acid (oleicacid), and 15% fatty acids saturated, 11% palmitic acid and 4% stearic acid (Esteves et al.,2010). The linoleic acids (ω6) and linolenic (ω3) found in soybean are considered essentialand are easily oxidized due to the presence of unsaturations. These fatty acids compete withthe enzymes involved in the reactions of desaturation and chain elongation. Although theseenzymes have a greater affinity for ω3 acids, the conversion of alpha-linolenic acid topolyunsaturated fatty acid of long chain is strongly influenced by levels of linoleic acid inthe diet. Thus, the ratio between daily intake of foods rich in ω6 and ω3, such as soybeans, isvery important in human nutrition (Martin et al., 2006).The lipid fraction of grain contains vitamin E isomers, α-tocopherol (42.0 to 291.0 mg/100g),γ-tocopherol (79.0 to 252.0 mg/100g) and δ-tocopherol (27.0 to 89.0 mg/100g) (Andrade,2010; Baumgartner et al., 2010); and small amounts of vitamin K (47 mcg/100g) and vitaminA (1.0 mcg/100g). There is also the presence of water soluble vitamins such as vitamin C(6.0 mg/100g), folates (375.0 mcg/100g), thiamin (0.9 mg/100 g), riboflavin (0.3 mg/100 g),pyridoxine (0.5 mg/100g), niacin (2.1 mg/100 g) (Lebiedzinska & Szefer, 2006; U.S.Department of Agriculture, 2009).2.1 Soy proteinsSoybean is the legume that presents the highest protein content and thus contributes to thesupply of essential amino acids and nitrogen to human and animals (Liu, 1997). The majorcomponents of soy proteins are storage proteins known as β-conglycinin (7S) and glycinin